[Python-ideas] Deterministic iterator cleanup

[Steven D'Aprano]

On Fri, Oct 21, 2016 at 11:03:51AM +0100, Paul Moore wrote:

> At the moment, the take home message for such users feels like it's
> "you might need to scatter preserve() around your code, to avoid the
> behaviour change described above, which you glazed over because it
> talked about all that coroutiney stuff you don't understand" :-)

I now believe that's not necessarily the case. I think that the message 
should be:

- If your iterator class has a __del__ or close method, then you need
  to read up on __(a)iterclose__.

- If you iterate over open files twice, then all you need to remember is 
  that the file will be closed when you exit the first loop. To avoid 
  that auto-closing behaviour, use itertools.preserve().

- Iterating over lists, strings, tuples, dicts, etc. won't change, since 
  they don't have __del__ or close() methods.


I think that covers all the cases the average Python code will care 
about.



-- 
Steve